Motor vehicle with disconnectable all-wheel drive system

ABSTRACT

A vehicle with a primary driveline that is configured to distribute rotary power to a first set of vehicle wheels and a power transmitting device that can be selectively operated to transmit rotary power to a secondary driveline. The power transmitting device has an input member, which is driven by the primary driveline, and an output member that is selectively coupled to the input member to receive rotary power therefrom. The secondary driveline comprises a differential, a pair of shafts, and a side shaft coupling that selectively interrupts power transmission between the differential and one of the shafts.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. patent application Ser. No. 13/223,811filed Sep. 1, 2011, which is a continuation of U.S. patent applicationSer. No. 12/537,394 filed Aug. 7, 2009 (now U.S. Pat. No. 8,042,642),which is a continuation-in-part of U.S. patent application Ser. No.12/191,699 entitled “Motor Vehicle With Disconnectable All-Wheel DriveSystem” filed Aug. 14, 2008 (now U.S. Pat. No. 8,047,323). Thedisclosure of the aforementioned patent applications is herebyincorporated by reference as if fully set forth in detail herein.

INTRODUCTION

The present invention generally relates to vehicle drivelines and moreparticularly to a vehicle driveline with a disconnectable all-wheeldrive system.

Many modern automotive vehicles, such as crossover vehicles, areavailable with an all-wheel drive (AWD) driveline that is based on afront-wheel drive (FWD) architecture. Unfortunately, such AWD drivelinestypically include components, such as the output of a power take-off,that are rotatably driven even when the driveline is operated in a modein which power is not transmitted through such components. Consequently,such AWD drivelines can be less fuel efficient (according to standardsestablished by the U.S. Environmental Protection Agency) than similarFWD drivelines by one or two miles per gallon.

Accordingly, there remains a need in the art for an improved AWDdriveline.

SUMMARY

In another form the teachings of the present disclosure provide avehicle with a primary driveline that is configured to distribute rotarypower to a first set of vehicle wheels, a power transmitting device anda secondary driveline that is configured to distribute power to a secondset of vehicle wheels. The power transmitting device has an inputmember, which is driven by the primary driveline, and an output memberthat is selectively coupled to the input member to receive rotary powertherefrom. The secondary driveline has a propshaft, an axle input, apair of axle shafts and at least one torque transfer device. Thepropshaft transmits rotary power between the output member of the powertransmitting device and the axle input. The axle shafts are rotatablycoupled to an output of the differential and configured to transmitrotary power to the second set of vehicle wheels. The at least onetorque transfer device is configured to selectively inhibit torquetransmission between the axle input and the second set of vehiclewheels.

In still another form, the present teachings provide a vehicle thatincludes a primary driveline and a power take-off unit (PTU). Theprimary driveline has a first differential that is configured todistribute power to a first set of vehicle wheels. The PTU has a PTUinput, a PTU output, a shift collar, an input gear, a driven gear, afirst bevel gear and a second bevel gear. The PTU output is disposedperpendicular to the PTU input. The shift collar is non-rotatably butaxially-slidably coupled to the PTU input. The input gear is rotatablymounted on the PTU input. The driven gear is non-rotatably coupled tothe first bevel gear and meshingly engaged to the input gear. The secondbevel gear is coupled for rotation with the PTU output and is meshinglyengaged to the first bevel gear. The shift collar is movable between afirst position, in which the input gear is not coupled for rotation withthe PTU input, and a second position in which the input gear is coupledfor rotation with the PTU input.

In yet another form, the teachings of the present disclosure provide avehicle having a first set of wheels. The vehicle includes a primarydriveline, which is configured to distribute rotary power to the firstset of vehicle wheels on a full-time basis, and a power transmittingdevice that has an input member and an output member. The input memberbeing driven by the primary driveline. The output member is selectivelycoupled to the input member to receive rotary power therefrom. The powertransmitting device includes a synchronizer having a collar that ismounted on a first intermediate member continuously driven by the inputmember. The collar is movable to engage a second intermediate member todrive the output member.

In a yet another form, the present teachings provide a vehicle thatincludes a primary driveline, a power transmitting device and asecondary driveline. The primary driveline is configured to distributerotary power to a first set of vehicle wheels. The power transmittingdevice has an input member, which is driven by the primary driveline,and an output member that is selectively coupled to the input member toreceive rotary power therefrom. The secondary driveline is configured todistribute power to a second set of vehicle wheels and includes apropshaft, an axle input, a differential, a pair of axle shafts and atleast side shaft coupling. The propshaft transmits rotary power betweenthe output member of the power transmitting device and the axle input.The axle shafts are rotatably coupled to an output of the differentialand configured to transmit rotary power to the second set of vehiclewheels. The at least one side shaft coupling is configured toselectively interrupt torque transmission between at least one componentof the differential and the second set of vehicle wheels. The powertransmitting device includes a synchronizer; and wherein thesynchronizer includes a collar that is mounted on a first intermediatemember continuously driven by the input member. The collar is axiallymovable to engage a second intermediate member that is coupled forrotation with the output member.

In a further form, the present teachings provide a vehicle having aprimary driveline, a power take-off unit (PTU), and a secondarydriveline. The primary driveline has a first differential that isconfigured to distribute power to a first set of vehicle wheels. The PTUhas a PTU input, a PTU output, a shift collar, an input gear, a drivengear, a first bevel gear and a second bevel gear. The PTU output isdisposed perpendicular to the PTU input. The shift collar isnon-rotatably but axially-slidably coupled to the PTU input. The inputgear is rotatably mounted on the PTU input. The driven gear isnon-rotatably coupled to the first bevel gear and meshingly engaged tothe input gear. The second bevel gear is coupled for rotation with thePTU output and meshingly engaged to the first bevel gear. The shiftcollar is movable between a first position, in which the input gear isnot coupled for rotation with the PTU input, and a second position inwhich the input gear is coupled for rotation with the PTU input. Thesecondary driveline is configured to distribute power to a second set ofvehicle wheels and includes a propshaft, a second differential, a pairof shafts and a torque transfer device. The propshaft transmits rotarypower between the PTU output and an input of the second differential.The second differential has a pair of differential outputs. A first oneof the shafts is rotatably coupled to a first one of the differentialoutputs. The torque transfer device has a clutch having a clutch input,which is rotatably coupled to a second one of the differential outputs,and a clutch output, which is rotatably coupled to a second one of theshafts. The clutch is configured to selectively interrupt powertransmission between the second one of the differential outputs and thesecond one of the shafts.

In yet another form, the present teachings provide a vehicle having aprimary driveline, a power take-off unit (PTU) and a secondarydriveline. The primary driveline has a first differential that isconfigured to distribute power to a first set of vehicle wheels. The PTUhas a PTU input, a PTU output and a synchronizer for selectivelyde-coupling the PTU output from the PTU input. The secondary drivelineis configured to distribute power to a second set of vehicle wheels andhas a propshaft, a second differential, a pair of shafts and a frictionclutch. The propshaft transmits rotary power between the PTU output andan input of the second differential. The second differential isrotatable about a differential axis and includes a pair of differentialoutputs. Each of the shafts is rotatably coupled to an associated one ofthe differential outputs and is configured to transmit rotary power tothe second set of vehicle wheels. The friction clutch is mounted aboutthe differential axis between the second differential and one of theshafts. The friction clutch is configured to selectively inhibit torquetransmission between the second differential and the one of the shafts.The synchronizer includes an axially shiftable member that is movablebetween a first position, in which the PTU input is not coupled forrotation with an intermediate gear, and a second position in which thePTU input is coupled for rotation with the intermediate gear to therebytransmit drive torque between the PTU input and the PTU output.

Further areas of applicability will become apparent from the descriptionprovided herein. It should be understood that the description andspecific examples are intended for purposes of illustration only and arenot intended to limit the scope of the present disclosure, itsapplication and/or uses in any way.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.Similar or identical elements are given consistent identifying numeralsthroughout the various figures.

FIG. 1 is a schematic illustration of a vehicle constructed inaccordance with the teachings of the present disclosure;

FIG. 2 is a section view of a portion of the vehicle of FIG. 1,illustrating a portion of the power take-off unit in more detail;

FIG. 3 is a schematic illustration of another vehicle constructed inaccordance with the teachings of the present disclosure;

FIG. 4 is a schematic illustration of yet another vehicle constructed inaccordance with the teachings of the present disclosure;

FIG. 5 is a sectional view of a portion of the vehicle of FIG. 4,illustrating a portion of the secondary driveline in more detail.

FIG. 6 is a schematic illustration of yet another vehicle constructed inaccordance with the teachings of the present disclosure;

FIG. 7 is a section view of a portion of the vehicle of FIG. 6,illustrating a portion of the secondary driveline in more detail;

FIG. 8 is a section view of another power take-off unit constructed inaccordance with the teachings of the present disclosure;

FIG. 9 is a section view of another power take-off unit constructed inaccordance with the teachings of the present disclosure;

FIG. 10 is a section view of another power take-off unit constructed inaccordance with the teachings of the present disclosure; and

FIG. 11 is a view similar to that of FIG. 10 but illustrating the ballramp clutch in an actuated condition.

DETAILED DESCRIPTION OF THE VARIOUS EMBODIMENTS

With reference to FIG. 1 of the drawings, a vehicle constructed inaccordance with the teachings of the present invention is generallyindicated by reference numeral 10. The vehicle 10 can include apowertrain 12 and a drivetrain 14 that can include a primary driveline16, a power take-off unit (PTU) 18, a secondary driveline 20 and acontrol system 22.

The powertrain 12 can include a prime mover 30, such as an internalcombustion engine or an electric motor, and a transmission 32, which canbe any type of transmission, such as a manual, automatic or continuouslyvariable transmission. The prime mover 30 can provide rotary power tothe transmission 32, which output rotary power to the primary driveline16 and the PTU 18.

The primary driveline 16 can include a first differential 40, which canbe driven by the transmission 32, and a pair of first axle shafts 42that can couple an output (not specifically shown) of the firstdifferential 40 to a first set of vehicle wheels 44.

With additional reference to FIG. 2, the PTU 18 can include a housing50, an input 52, which can be housed in the housing 50 and coupled forrotation with an output 54 of the transmission 32 (e.g., via a set ofmating spline teeth 56), an output 58, which can be rotatably supportedon a set of bearings (not shown) that are received in the housing 50,and a synchronizer 60. The synchronizer 60 can include an axiallymovable member 62 that can be moved between a first position (shown inphantom line in FIG. 2), in which the output 58 is not driven by theinput 52, and a second position (shown in solid line in FIG. 2) in whichthe output 58 is driven by the input 52. The synchronizer 60 can alsoinclude an actuator, such as a linear actuator 70 for moving the axiallymovable member 62 from the first position to the second position, fromthe second position to the first position, or both.

In the example provided, the synchronizer 60 further includes an inputgear 80, a driven gear 82, a first bevel gear 84 and a second bevel gear86. The input gear 80 can be disposed coaxially on the output 54 of thetransmission 32 on a set of bearings 90 and can include a plurality ofgear teeth 92 and a plurality of first coupling teeth 94. The drivengear 82 can include a plurality of gear teeth 96, which can be inmeshing engagement with the gear teeth 92 of the input gear 80, and canbe supported via a set of bearings 98 for rotation in the housing 50.The first bevel gear 84 can be coupled for rotation with the driven gear82 (e.g., the driven gear 82 and the first bevel gear 84 can beintegrally formed as is shown in the example provided) and can include afirst set of bevel gear teeth 100. The second bevel gear 86 can includea second set of bevel gear teeth 102 that can be meshingly engaged tothe first set of bevel gear teeth 100. The output 58 can be coupled forrotation with the second bevel gear 86 (e.g., the second bevel gear 86and the output 58 can be integrally formed as is shown in the exampleprovided).

The linear actuator 70 can be any type of linear actuator and can beelectrically, mechanically, hydraulically and/or pneumatically operated.In the particular example provided, the linear actuator 70 includes asolenoid 110, a shift fork 112 and a biasing spring 114. The solenoid110 can be coupled to the housing 50 and can conventionally include acoil 116 and a plunger 118. The coil 116 can be selectively energized bythe control system 22 to generate a magnetic field that can cause theplunger 118 to move from a first position (shown in phantom line in FIG.2) to a second position (shown in solid line in FIG. 2). The shift fork112 can include an arm 120, which can be fixedly coupled to the plunger118, and a generally C-shaped yoke 122 that can be disposed in (andextend around a portion of the circumference of) a groove 124 that isformed about the axially movable member 62. The biasing spring 114 canbe disposed between the housing 50 and the arm 120 of the shift fork 112and can apply a force to the shift fork 112 to bias the plunger 118toward the first position. In the particular example provided, theaxially movable member 62 includes a plurality of internal teeth 130that are meshingly engaged and slidably disposed on corresponding secondcoupling teeth 132 formed on the outer peripheral surface of the input52.

When the coil 116 is energized to cause the plunger 118 to move from thefirst position to the second position, the shift fork 112 will moveaxially by a corresponding amount, causing the axially movable member 62to slide along the second coupling teeth 132 and into engagement withthe first coupling teeth 94 that are formed on the input gear 80 tothereby rotatably couple the input gear 80 with the input 52 so thatdrive torque may be transmitted therebetween. When the coil 116 isde-energized, the biasing spring 114 will urge the plunger 118 towardthe second position and cause the shift fork 112 (and the axiallymovable member 62) to move axially by a corresponding amount. Theaxially movable member 62 will slide on the second coupling teeth 132and will disengage the first coupling teeth 94 to thereby rotatablyde-couple the input gear 80 from the input 52 so that drive torque maynot be transmitted therebetween.

While the linear actuator 70 has been illustrated as including asolenoid 110 and a shift fork 112, those of ordinary skill in the artwill be appreciated that various other types of devices can be employed,including ball or lead screws and pressure cylinders. Also, those ofordinary skill will appreciate that while the biasing spring 114 isconfigured to generate a biasing force that tends to decouple theaxially movable member 62 from the input gear 80 so that the vehicle 10is normally operated in a two-wheel drive mode (e.g., front wheel drivemode), the biasing spring 114 could be located so as to generate abiasing force that tends to couple the axially movable member 62 to theinput gear 80 so that the vehicle 10 is normally operated in anall-wheel drive mode.

The secondary driveline 20 can include a propshaft 150, a seconddifferential 152, a pair of second axle shafts 154 and at least onetorque transfer device 156. A first end of the propshaft 150 can becoupled for rotation with the output 58 of the PTU 18, while a secondend of the propshaft 150 can be coupled for rotation with an input 160of the torque transfer device 156. The torque transfer device 156 can beemployed to selectively transmit rotary power to an input pinion 170.Power received by the input pinion 170 is transmitted through a ringgear 172 to the second differential 152 and output from the seconddifferential to the second axle shafts 154 to thereby couple the seconddifferential 152 to a second set of vehicle wheels 174.

In the particular example provided, the at least one torque transferdevice 156 includes a clutch 180, such as a conventionalelectrically-controlled friction clutch, that is disposed between thesecond end of the propshaft 150 and the input pinion 170 of the seconddifferential 152. The clutch 180 can be controlled by the control system22 to operate in a first mode, in which the second end of the propshaft150 is rotatably de-coupled from the input pinion 170 of the seconddifferential 152, and a second mode in which the second end of thepropshaft 150 is rotatably coupled to the input pinion 170 of the seconddifferential 152.

The control system 22 can include a first sensor 190, a second sensor192 and a controller 194. The first sensor can be configured to sense arotational speed of a component associated with the primary driveline16, such as the output 54 (FIG. 2) of the transmission 32, and toresponsively generate a first sensor signal in response thereto. Thesecond sensor can be configured to sense a rotational speed of acomponent associated with the secondary driveline 20, such as the input160 of the torque transfer device 156, and to responsively generate asecond sensor signal in response thereto. The controller 194 can controloperation of the at least one torque transfer device 156 based in parton the first and second sensor signals.

In operation, the vehicle 10 is normally operated in a two-wheel drivemode (e.g., front wheel drive mode) in which the output 58 of the PTU 18is de-coupled from the input 52 of the PTU 18 so that substantially allof the rotary power provided from the powertrain 12 is transmitted tothe first differential 40. It will be appreciated that when the vehicle10 is operated in this mode, only the axially movable member 62 of thePTU 18 will be driven by the transmission 32. Consequently, the vehicle10 will experience only minor losses relative to a conventionaltwo-wheel drive vehicle (not shown) due to the additional mass of thePTU 18 and the secondary driveline 20, as well as from the rotation ofthe second axle shafts 154 and the second differential 152.

When all-wheel drive is desired, the control system 22 can be activatedvia a suitable input, which can include a manual (driver requested)input and/or an input generated by the controller 194 in response to thedetection of a predetermined event (e.g., slipping of the first set ofvehicle wheels 44). The controller 194 can transmit a signal to thelinear actuator 70 to energize the coil 116 to cause the axially movablemember 62 to be moved into engagement with the first coupling teeth 94to thereby rotatably couple the input gear 80 to the input 52 of the PTU18. The controller 194 can evaluate the first and second sensor signalsto determine whether the rotational speed of a component associated withthe secondary driveline 20 (i.e., the input 160 of the torque transferdevice 156 in the example provided) is rotating at a speed that is equalto or within a predetermined tolerance of the rotational speed of thecomponent associated with the primary driveline 16 (i.e., the output ofthe transmission 32 in the example provided). The controller 194 canselectively activate the torque transfer device 156 to transmit rotarypower to the second set of vehicle wheels 174 a when the rotationalspeeds of the components of the primary and secondary drivelines 16 and20 are rotating at equal speeds or at speeds that are within thepredetermined tolerance.

In the example of FIG. 3, the vehicle 10 a is generally similar to thevehicle 10 of FIG. 1, except that the at least one torque transferdevice 156 a includes a pair of automatic wheel hubs 200 that can beoperated to selectively couple the second axle shafts 154 a to thesecond set of vehicle wheels 174, the propshaft 150 a is coupleddirectly to the input pinion 170 a of the second differential 152, andthe second sensor 192 a is configured to sense a rotational speed of theinput pinion 170 a and responsively produce a second sensor signal.

With additional reference to FIG. 2, the vehicle 10 a can be normallyoperated in a two-wheel drive mode (e.g., front wheel drive mode) inwhich the output 58 of the PTU 18 is de-coupled from the input 52 of thePTU 18 so that substantially all of the rotary power provided from thepowertrain 12 is transmitted to the first differential 40. It will beappreciated that when the vehicle 10 a is operated in this mode, onlythe axially movable member 62 of the PTU 18 will be driven by thetransmission 32. Moreover, rotation of the second set of vehicle wheels174 will not cause corresponding rotation of the second differential152. Consequently, the vehicle 10 a will experience only minor lossesrelative to a conventional two-wheel drive vehicle (not shown) due tothe additional mass of the PTU 18 and the secondary driveline 20 a, aswell as from the rotation of the second axle shafts 154 a and the seconddifferential 152.

When all-wheel drive is desired, the control system 22 a can beactivated via a suitable input, which can include a manual (driverrequested) input and/or an input generated by the controller 194 a inresponse to the detection of a predetermined event (e.g., slipping ofthe first set of vehicle wheels 44). The controller 194 a can transmit asignal to the linear actuator 70 to energize the coil 116 to cause theaxially movable member 62 to be moved into engagement with the firstcoupling teeth 94 to thereby rotatably couple the input gear 80 to theinput 52 of the PTU 18. The controller 194 a can evaluate the first andsecond sensor signals to determine whether the rotational speed of acomponent associated with the secondary driveline 20 a (i.e., the inputpinion 170 a in the example provided) is rotating at a speed that isequal to or within a predetermined tolerance of the rotational speed ofthe component associated with the primary driveline 16 (i.e., the output54 of the transmission 32 in the example provided). The controller 194can selectively activate the at least one torque transfer device 156(i.e., the automatic wheel hubs 200 in the example provided) to transmitrotary power to the second set of vehicle wheels 174 when the rotationalspeeds of the components of the primary and secondary drivelines 16 and20 a are rotating at equal speeds or at speeds that are within thepredetermined tolerance.

In the example of FIGS. 4 and 5, the vehicle 10 b is generally similarto the vehicle 10 of FIG. 1, except that the at least one torquetransfer device 156 b includes a friction clutch 300 that can beoperated to selectively couple a first one 154 b-1 of the second axleshafts 154 b to the second differential 152, the propshaft 150 b iscoupled directly to the input pinion 170 b of the second differential152, and the second sensor 192 b is configured to sense a rotationalspeed of the input pinion 170 b and responsively produce a second sensorsignal.

With additional reference to FIG. 2, the vehicle 10 b can be normallyoperated in a two-wheel drive mode (e.g., front wheel drive mode) inwhich the output 58 of the PTU 18 is de-coupled from the input 52 of thePTU 18 so that substantially all of the rotary power provided from thepowertrain 12 is transmitted to the first differential 40. It will beappreciated that when the vehicle 10 b is operated in this mode, onlythe axially movable member 62 of the PTU 18 will be driven by thetransmission 32.

When all-wheel drive operation is desired, the control system 22 b canbe activated via a suitable input, which can include a manual (driverrequested) input and/or an input generated by the controller 194 b inresponse to the detection of a predetermined event (e.g., slipping ofthe first set of vehicle wheels 44). The controller 194 b can transmit asignal to the linear actuator 70 to energize the coil 116 to cause theaxially movable member 62 to be moved into engagement with the firstcoupling teeth 94 to thereby rotatably couple the input gear 80 to theinput 52 of the PTU 18. The controller 194 b can evaluate the first andsecond sensor signals to determine whether the rotational speed of acomponent associated with the secondary driveline 20 b (i.e., the inputpinion 170 b in the example provided) is rotating at a speed that isequal to or within a predetermined tolerance of the rotational speed ofthe component associated with the primary driveline 16 (i.e., the outputof the transmission 32 in the example provided). The controller 194 bcan selectively activate the at least one torque transfer device 156 b(i.e., the friction clutch 300 in the example provided) to transmitrotary power to the second set of vehicle wheels 174 when the rotationalspeeds of the components of the primary and secondary drivelines 16 and20 b are rotating at equal speeds or at speeds that are within thepredetermined tolerance.

In the example of FIGS. 6 and 7, the vehicle 10 c is generally similarto vehicle 10 b of FIG. 4, except that: the second differential 152 clacks an internal gearset (i.e., pinion gears and side gears) and canconsist of a differential case 176 c that is coupled for rotation withthe ring gear 172; the at least one torque transfer device 156 cincludes a friction clutch 400 that can be selectively operated tocouple the second axle shafts 154 c-1 and 154 c-2 to the differentialcase 176 c; the propshaft 150 c is coupled directly to the input pinion170 c of the secondary driveline 20 c; the second sensor 192 c isconfigured to sense a rotational speed of the input pinion 170 c andresponsively produce a second sensor signal; a third sensor 196 c isconfigured to sense a pressure in the friction clutch 400 andresponsively produce a third sensor signal; and a fourth sensor 198 c isconfigured to sense a position of the axially moveable member 62 (FIG.2) and responsively generate a fourth sensor signal.

With specific reference to FIG. 7, the friction clutch 400 can include aclutch housing 502, a clutch input member 402, a first clutch outputmember 504, a second clutch output member 506, a first clutch pack 404,a second clutch pack 406, a spacer 408 and an engagement mechanism 410.The clutch housing 500 can define a cavity 510 into which the first andsecond clutch packs 404 and 406, the spacer 408 and the engagementmechanism 410 can be at least partly housed. A through-bore 512 canextend through the clutch housing 500. In the particular exampleprovided, the clutch housing 500 is a discrete component, but it will beappreciated that the clutch housing 500 could alternatively beintegrally formed with the housing 514 in which the differential case176 c is rotatably supported.

The clutch input member 402 can be supported for rotation within theclutch housing 500 (e.g., via a first set of bearings 518) and can becoupled for rotation with the differential case 176 c. In the particularexample illustrated, the clutch input member 402 comprises a shaftportion 520, which can extend through one side of the through-bore 512in the clutch housing 502, and an annular member 522 that can bereceived in the clutch cavity 510 and coupled for rotation with theshaft portion 520. The annular member 522 can comprise a plurality ofcircumferentially spaced apart internal spline teeth 524 that can extendgenerally parallel to an axis 526 about which the clutch input member402 rotates.

The first clutch output member 504 can include a first plate structure540, which can be received in the clutch cavity 510, and a firstcoupling portion 542 that can be employed to couple an associated one ofthe second axle shafts 154 c-1 to the first plate structure 540 forrotation therewith. A plurality of external spline teeth 544 can beformed about the perimeter of the first plate structure 540. Theexternal spline teeth 544 can extend generally parallel to therotational axis 526 of the clutch input member 402. The first couplingportion 542 can be a shaft-like structure that can be coupled forrotation with the plate structure 540. The first coupling portion 542can be received in the through-bore 512 in the clutch housing 502 andcan be supported for rotation about the axis 526 via a set of bearings548. The first coupling portion 542 can include a coupling section 550that can be drivingly coupled to an associated one of the second halfshafts 154 c-1. In the particular example, the coupling section 550comprises a plurality of external splines 554 that are matingly engagedby a plurality of internal splines 556 formed about the perimeter of anaperture 558 in an associated one of the second half shafts 154 c-1. Itwill be appreciated, however, that other means may be employed forcoupling the plate structure 540 with an associated one of the secondaxle shafts 154 c-1.

The second clutch output member 506 can similarly include a second platestructure 560, which can be received in the clutch cavity 510, and asecond coupling portion 562 that can be employed to couple an associatedone of the second axle shafts 154 c-2 to the second plate structure 560for rotation therewith. A plurality of external spline teeth 564 can beformed about the perimeter of the second plate structure 560. Theexternal spline teeth 564 can extend generally parallel to therotational axis 526 of the clutch input member 402. The second couplingportion 562 can be a non-circular aperture into which a matingly shapedend 566 of an associated one of the second axle shafts 154 c-2 can bereceived. In the particular example provided, the non-circular aperturein the second coupling portion 562 and the matingly shaped end 566 ofthe associated one of the second axle shafts 154 c-2 employ a pluralityof mating splines that extend generally parallel to the rotational axis526 to permit the associated one of the second half shafts 154 c-2 to beslid into engagement with the second clutch output member 506.

The second clutch pack 406 can be generally similar to the first clutchpack 404 and as such, only the first clutch pack 404 will be discussedin detail. The first clutch pack 404 can include a plurality of firstclutch plates 570 and a plurality of second clutch plates 572. The firstclutch plates 570 can include a splined internal aperture 574 while thesecond clutch plates 572 can include a splined external perimeter 576.It will be appreciated that the configuration of the first and secondclutch plates 570 and 572 could be reversed, however. The first andsecond clutch plates 570 and 572 can be interleaved such that each firstclutch plate 570 can be adjacent to at least one of the second clutchplates 572 (i.e., adjacent to one of the second clutch plates 572 orreceived between a pair of the second clutch plates 572). The spacer 408can be received between the first and second clutch packs 404 and 406.

The engagement mechanism 410 can be selectively operated to apply aforce to the first and second clutch packs 404 and 406 to engage thefirst clutch plates 570 and the second clutch plates 572 to one anotherto transmit rotary power between the clutch input member 402 and thefirst and second clutch output members 504 and 506. The engagementmechanism 410 can include a piston 580 that can be translated via fluidpressure (e.g., hydraulic, pneumatic) from a fluid pressure source 582to apply force to the first and second clutch packs 404, 406 (i.e., toactuate the first and second clutch packs 404, 406). Fluid pressuredelivered to the piston 580 can be controlled by a controller 584 and anelectronically controlled valve assembly 586 that can be configured tovary the pressure that acts on the piston 580. Alternatively, the piston580 can be translated by an electrically-operated linear motor, such asa solenoid, to actuate the first and second clutch packs 404, 406.

To operate the vehicle 10 c in a two-wheel drive mode, the frictionclutch 400 can be deactivated or disengaged to decouple the clutch inputmember 402 from the first and second clutch output members 504 and 506to thereby decouple the second set of vehicle wheels 174 from the seconddifferential 152 c.

If desired, the friction clutch 400 can be operated to limit the torquethat is transmitted through the first and second clutch packs 404, 406.In this regard, the vehicle control system 22 c can operate theengagement mechanism 410 to selectively vary an engagement force appliedby the piston 580 onto the first and second clutch packs 404, 406 so asto permit the first and second clutch output members 504, 506 to sliprelative to the clutch input member 402 should the torque transmitted toan associated one of the wheels of that second set of vehicle wheels 174exceed a clutch torque produced in the respective clutch pack when agiven engagement force is applied thereto.

The control system 22 c can be generally similar to the control system22 described above and illustrated in FIG. 1, except that it can furtherinclude a third sensor 196 c and a fourth sensor 198 c that can becoupled to the controller 194 c. The third sensor 196 c can beconfigured to sense a characteristic related to the force applied by thepiston 580, such as a fluid pressure (in situations where the piston 580is moved via a pressurized fluid), and responsively generate a thirdsensor signal. It will be appreciated that the third sensor signal canbe employed for various reasons, including a feedback loop forcontrolling the engagement force, for fault detection, and/or forverification that the friction clutch 400 is engaged. The fourth sensor198 c can be configured to sense a position of a component in the PTU18, such as the axially moveable member 62, and responsively generate afourth sensor signal that can be employed to identify situations wherethe PTU 18 is or is not operating to transmit rotary power to thesecondary driveline 20 c.

With reference to FIG. 8, another PTU constructed in accordance with theteachings of the present disclosure is generally indicated by referencenumeral 18 d. The PTU 18 d can be generally similar to the PTU 18 ofFIGS. 1 and 2, except that the PTU 18 d can employ a dog clutch 52 d forselectively coupling the output 54 of transmission 32 to the input gear80. The dog clutch 52 d can include a first clutch portion 502 and asecond clutch portion 504. The first clutch portion 502 can include abody 506 and a plurality axially extending teeth 508. The body 506 canhave a splined aperture 510 which can be coupled for rotation with theoutput 54, and a circumferential groove 512 that can be configured toaccept the shift fork 112 of the linear actuator 70. The second clutchportion 504 can include a body 516 and a plurality of axially extendingteeth 518. The body 516 can be coupled to the input gear 80 for rotationtherewith and can have an aperture 520 into which one of the bearings 90can be received. Alternatively, the body 516 and the input gear 80 canbe integrally formed. The first clutch portion 502 of the dog clutch 52d can be selectively engaged with the second clutch portion 504 by thelinear actuator 70. The linear actuator 70 can translate the shift fork112, which is received in the circumferential groove 512, to axiallymove the first clutch portion 502 between a first position (shown inphantom line in FIG. 8), in which the teeth 508 and 518 are not engagedto one another, and a second position (shown in solid line in FIG. 8),in which the teeth 508 and 518 are engaged to one another to transmitrotary power therebetween to drive the output 58.

With reference to FIG. 9, another PTU constructed in accordance with theteachings of the present disclosure is generally indicated by referencenumeral 18 e. The PTU 18 e is generally similar to the PTU 18 d of FIG.8, except that the PTU 18 e can employ a cone clutch 52 e forselectively coupling the output 54 of transmission 32 to the input gear80. The cone clutch 52 e can include a first clutch portion 602 and asecond clutch portion 604. The first clutch portion 602 can include abody 606 and a conical projection 608. The first clutch portion 602 canhave a splined aperture 610 that can be coupled for rotation with theoutput 54. The body 606 can have a circumferential groove 612 to acceptthe shift fork 112 of the linear actuator 70. The second clutch portion604 can include a body 616 and a conical aperture 618 to accept theconical projection 608 of the first clutch portion 602. The body 616 canbe coupled to the input gear 80 and can have an aperture 620 into whichone of the bearings 90 can be received. Alternatively, the body 616 andthe input gear 80 can be integrally formed. The first clutch portion 602of the cone clutch 52 e can be selectively engaged with the secondclutch portion 604 by the linear actuator 70. The linear actuator 70 cantranslate the shift fork 112, which can be located in thecircumferential groove 612, to axially move the first clutch portion 602between a first position (shown in phantom line in FIG. 9), in which theconical projection 608 and the conical aperture 618 are not in contact,and a second position (shown in solid line in FIG. 9), in which theconical projection 608 is fittingly accepted by the conical aperture 618to couple the first and second clutch portions 602, 604 to drive theoutput 58.

With reference to FIGS. 10 and 11, another PTU constructed in accordancewith the teachings of the present disclosure is generally indicated byreference numeral 18 f. The PTU 18 f is generally similar to the PTU 18d of FIG. 8, except that the PTU 18 f can employ a ball ramp clutch 52 ffor selectively coupling the output 54 of transmission 32 to the inputgear 80. The ball ramp clutch 52 f can generally include a first clutchportion 702 and a second clutch portion 704. The first clutch portion702 can include an activation ring 706 and a control ring 708 with aplurality of rolling elements 710 therebetween, a first friction plate712, and a retainer ring 714. The activation ring 706, the control ring708, the first friction plate 712, and the retainer ring 714 can have anaperture therethrough. The activation ring 706 and the control ring 708can be disposed coaxially on the output 54 of the transmission 32 on aset of bearings 709. The first friction plate 712 can be coupled to theoutput 54 by splines 716. The retainer ring 714 can maintain thealignment of the components of the first clutch portion 702. The secondclutch portion 704 can include a second friction plate 718. The secondfriction plate 718 can be coupled to the input gear 80 or be integrallyformed therewith. The first clutch portion 702 of the ball ramp clutch52 f can be selectively engaged with the second clutch portion 704 by anactuator (not shown), such as an electric coil. The actuator can operateto rotate the activation ring 706 to axially increase the distancebetween the activation ring 706 and the control ring 708 by the actionof the rolling elements 710 rolling on ramped grooves during therotation. As the activation ring 706 rotates (or alternatively thecontrol ring), the rolling elements 710 roll up ramped grooves in theactivation ring 706 and control ring 708 to space the rings 706, 708apart. Axial movement of the activation ring 706 causes the activationring 706 to push the first friction plate 712 to thereby frictionallyengage the second friction plate 718 (the engaged first and secondfriction plates 712, 718 are illustrated in FIG. 11), thus engaging thefirst clutch portion 702 and the second clutch portion 704 to drive theoutput 58.

It will be appreciated that the above description is merely exemplary innature and is not intended to limit the present disclosure, itsapplication or uses. While specific examples have been described in thespecification and illustrated in the drawings, it will be understood bythose of ordinary skill in the art that various changes may be made andequivalents may be substituted for elements thereof without departingfrom the scope of the present disclosure as defined in the claims.Furthermore, the mixing and matching of features, elements and/orfunctions between various examples is expressly contemplated herein sothat one of ordinary skill in the art would appreciate from thisdisclosure that features, elements and/or functions of one example maybe incorporated into another example as appropriate, unless describedotherwise, above. Moreover, many modifications may be made to adapt aparticular situation or material to the teachings of the presentdisclosure without departing from the essential scope thereof.Therefore, it is intended that the present disclosure not be limited tothe particular examples illustrated by the drawings and described in thespecification as the best mode presently contemplated for carrying outthe teachings of the present disclosure, but that the scope of thepresent disclosure will include any embodiments falling within theforegoing description and the appended claims.

What is claimed is:
 1. A vehicle comprising: a primary driveline that isconfigured to distribute rotary power to a first set of vehicle wheels;a power transmitting device having an input member and an output member,the input member being driven by the primary driveline, the outputmember being selectively coupled to the input member to receive rotarypower therefrom; and a secondary driveline that is configured todistribute power to a second set of vehicle wheels, the secondarydriveline having a propshaft, an axle input, a differential, a pair ofaxle shafts and at least one side shaft coupling, the propshafttransmitting rotary power between the output member of the powertransmitting device and the axle input, the axle shafts being rotatablycoupled to an output of the differential and configured to transmitrotary power to the second set of vehicle wheels, the at least one sideshaft coupling being configured to selectively interrupt torquetransmission between at least one component of the differential and thesecond set of vehicle wheels; wherein the power transmitting deviceincludes a synchronizer; and wherein the synchronizer includes a collarthat is mounted on a first intermediate member continuously driven bythe input member, the collar being axially movable to engage a secondintermediate member that is coupled for rotation with the output member.2. The vehicle of claim 1, wherein the at least one side shaft couplingcomprises a friction clutch.
 3. The vehicle of claim 2, wherein thepower transmitting device is a power take off.
 4. The vehicle of claim3, wherein the friction clutch includes a clutch member, first andsecond clutch packs having respective inputs driven by the clutch memberand an engagement mechanism for selectively applying an engagement forceto the first and second clutch packs to engage the friction clutch. 5.The vehicle of claim 4, further comprising a sensor coupled to thefriction clutch, the sensor being configured to sense a characteristicindicative of the engagement force and generate a sensor signal inresponse thereto.
 6. The vehicle of claim 5, wherein the axle inputcomprises an input pinion.
 7. The vehicle of claim 1, wherein the atleast one side shaft coupling comprises a first clutch and a secondclutch, wherein the first clutch is configured to selectively transmittorqued between the differential and a first shaft of the pair of axleshafts and wherein the second clutch is configured to selectivelytransmit torque between the differential and a second shaft of the pairof axle shafts.